In response to the development of cataractous lenses, it has become common to replace the lens with an intraocular lens (IOL) in a surgical procedure. In order to reduce the trauma to the eye in cataract surgery, it is desirable to keep the incision through which the surgical procedure is conducted as small as possible. With the development of phacoemulsification surgery, in which the lens is fragmented by ultrasonic vibrations and the fragments aspirated through a small cannula, it has become possible to remove a lens through an incision no larger than 2-3 millimeters. However, since an IOL is typically at least six millimeters in diameter, an incision at least that large has to be made to permit the insertion of the IOL. In order to permit the use of the desirable small incision technique, various flexible, distortable, and inflatable IOLs have been devised.
Juergens, U.S. Pat. No. 4,619,662, discloses a collapsible intraocular lens with a hollow interior which can be evacuated to cause the lens to collapse to a relatively small size. The collapsed lens can then be inserted into the eye through a relatively small incision. After insertion, the interior of the lens is filled with an elastomer to expand the lens to the proper shape and dimension.
Mazzocco, U.S. Pat. No. 4,573,998, discloses a deformable intraocular lens that can be rolled, folded, or stretched to fit through a relatively small incision. The deformable lens is inserted while it is held in its distorted configuration, then released inside the chamber of the eye, whereupon the elastic property of the lens causes it to resume its molded shape. As suitable materials for the deformable lens, Mazzocco discloses polyurethane elastomers, silicone elastomers, hydrogel polymer compounds, organic or synthetic gel compounds and combinations thereof.
Keates et al., U.S. Pat. No. 4,619,657, disclose a flexible intraocular lens holder made from a flexible inert polymer, such as silicone rubber, which contains pockets for receiving individual lenses which are small enough to fit through a relatively small incision. The lens holder is folded or rolled and inserted through a small incision and thereafter several of the small lenses are inserted through the incision and into the pockets in the lens holder to form a composite intraocular lens.
A number of these known methods of providing an intraocular lens which can be inserted through a small incision have suffered from the excessive complexity of inflatable lenses or composite lenses. The deformable intraocular lenses are simpler to manufacture and use; however, when they are made of materials hitherto employed, such as polyurethane elastomers and silicone elastomers, which have a relatively low refractive index, they must be relatively thick in order to provide a lens of the proper refractive power. The thicker the lens, the more difficult it is to deform or distort it into a shape which will fit through a small incision. Furthermore, the distortion required to force a thick lens through a small incision may exceed its elastic properties so that it breaks or will not recover its original shape when released within the eye. Therefore, lenses made from such materials are somewhat limited as to the minimum size to which they may be deformed.
Accordingly, there is a need for a material, with a relatively high refractive index, which can be used to form a flexible intraocular lens which can be simply rolled or folded into a configuration which will fit through a small incision.